1. Field of the Invention
The present invention relates to a system for detection of surgical implements; and more particularly, to a method and means for detecting a marked surgical implement such as a sponge, scissors, clamp, or other instrument within a surgical wound in human or animal tissue.
2. Description of the Prior Art
During the course of a surgical operation it is generally necessary for a variety of articles, such as surgical sponges, gauzes, instruments and the like, to be placed into a wound cavity. Despite rigorous precautions designed to retrieve these items and ensure their removal prior to completion of the surgical procedure and closure of the surgical incision, such items are sometimes inadvertently lost during surgery and remain within the patient. When this occurs, serious consequences often ensue. The patient may suffer pain, infection, intestinal obstruction, and even death. An additional invasive surgical procedure is then necessary to remove the foreign object in order to prevent serious, and possibly fatal, consequences to the patient. The problem of retained surgical implements has been recognized since the earliest days of surgery. The procedures traditionally employed to prevent post-surgical implement retention include manual search of the wound by the surgeon prior to closure and a careful accounting for all materials inserted and removed from the wound. This accounting function is customarily carried out by the operating room staff, usually the circulating nurse. Notwithstanding these precautionary measures the accidental retention of surgical implements continues to occur to this day with disturbing regularity, even in highly respected institutions. Surgeons and related medical professionals regard this unfortunate mishap as a major unsolved problem.
At present, physical count combined with manual search remain the primary procedure used for detecting retained surgical implements. Nevertheless, the above-mentioned failures of the conventional procedures have led to other approaches, such as the use of x-ray methods. Most surgical instruments are composed of metal, and are easily visible on x-ray. Sponges are generally made to bear a radiopaque component to make them also visible on x-ray. However, intra-operative x-rays are not routinely performed before closure of the incision for several reasons: They entail the risk of extension of operative time and anesthesia, along with undesirable expense, inconvenience, and radiation exposure. Postoperative x-rays are subject to some of the same disadvantages and are not generally done unless there is a specific question of a retained implement in a given case. Moreover, even when postoperative x-rays are obtained, retained surgical implements are still overlooked in many cases, owing to the presence of other competing shadows on the film. If a retained article is detected, a timely second operation is required to effect its removal, notwithstanding the further trauma to the patient. The severity of the problem clearly warrants efforts that allow the aforementioned consequences to be avoided altogether by ensuring removal of the offending articles before surgery is completed, not at a later point.
Over the years many efforts have been made to prevent the accidental retention of surgical implements. It has been suggested that the implements be provided with a radioactive tracer. This technique, disclosed by U.S. Pat. No. 2,740,405 to Riordan, is subject to obvious hazards associated with use, storage and disposal of radioactive materials and has never gained general acceptance
It has also been proposed that surgical sponges be marked with a flexible plastic impregnated with either paramagnetic or ferromagnetic materials in the form of powders. Detection of these marked sponges is accomplished by a metal detector. This method, taught by U.S. Pat. No. 3,422,816 to Robinson et al., provides very small signals difficult to detect over the width of a patient's body. In addition, the Robinson et al. technique provides no discrimination against other metal objects, such as a stent or staple which, though present within the surgical wound, are appointed for retention therewithin.
Yet another proposal, advanced by U.S. Pat. No. 3,587,583 to Greenberg, involves use of surgical sponges marked with magnetized particles whose presence is detectable with magnetodiodes. In practice, however, the magnetic field generated by these particles is too small to be readily detected by the diodes.
U.S. Pat. No. 4,114,601 to Ables discloses the use of a small transponder fixed to a surgical sponge or instrument. This transponder exhibits gyromagnetic resonance at preselected frequencies. Detection is accomplished by nonlinear mixing of two frequencies impinging upon the transponder. The gyromagnetic resonance effect disclosed by Ables is a high-frequency phenomenon, existing at frequencies of the order of about 5 gigahertz (5,000,000,000 cycles/sec). These frequencies, known as microwaves, are absorbed readily by tissue. In use of the Ables-type transponder, the energy developed goes primarily into heating tissue, rather than exciting the transponder into gyromagnetic resonance.
U.S. Pat. No. 4,510,489 to Anderson et al. discloses an article surveillance system especially useful in the protection of articles from theft from retail businesses and similar institutions. The system employs a magnetomechanically resonant marker and detection electronics for sensing the presence of the marker.
U.S. Pat. Nos. 5,057,095, 5,107,862, 5,190,059, 5,329,944, 5,105,829, and 5,188,126 to Fabian et al. disclose the use of various technologies to detect surgical implements marked with a tag and left within the surgical wound after completion of surgery and prior to closing the wound. In these patents, the detection apparatus is utilized in the operating room, since detection is accomplished before closure of the wound. While these systems are effective in detecting marked surgical implements, the electromagnetic fields generated during operation of the systems may interfere with other medical electronics, such as heart monitors, extant in the operating room. Since such devices require operating room personnel to diligently scan each patient, the potential for operator error is always present. The units had two components, one of which was designed to be intrinsic to the operating table itself. Therefore, to assure reliable detection of surgical implements during an operation, a separate unit is required in each operating room, entailing high cost and space requirements.
Thus, up to the present time, the optimal means for detecting post-operatively retained surgical implements, though addressed by numerous workers in the art, have yet to be found. Instead, the detection systems heretofore proposed each have significant drawbacks allowing for correction.